1. Field of the Invention
The present invention relates to a semiconductor memory device and a semiconductor device. More particularly, the invention relates to a layout geometry of a semiconductor memory device which contributes to improvements in the performance and wiring efficiency of the semiconductor memory device serving as a hard macro and to ease of connections with peripheral circuits.
2. Description of the Related Art
In the field of the manufacture of semiconductor devices, their high degree of integration resulting from the advance of microfabrication technology has been recently accelerating more and more together with competition among semiconductor manufacturers. Among them, system LSIs fabricated by providing a large-capacity memory on individual chips together with a microprocessor, an ASIC, a custom logic, or the like are a product line on which the manufacturers focus their efforts as a key device which allows them to offer a high added value which decides the performance and differentiation of products to which the LSIs are mounted.
Since it is said that memories classified as ROMs and SRAMs are also required to come in various sizes as hard macros in terms of the design of these semiconductor devices called system LSIs and since it is easy to place those memories in combination in the regions of logic circuits in terms of their layout design, those memories are required to have quadrilateral shapes as a de facto basic specification.
In the mounting of large-capacity DRAMs as well, they have been required to have the shape of such a quadrilateral as a basic specification. Therefore the configuration of a basic circuit of a semiconductor device including a DRAM will be described below with reference to FIG. 9.
In FIG. 9, reference numeral 101 denotes a memory cell region in which memory cells are arranged in the form of a matrix, reference numeral 102 denotes a row decoder circuit which selectively points to a row in the memory cell region 101, reference numeral 103 denotes a column decoder circuit which selectively points to a column in the memory cell region 101, reference numeral 104 denotes a sense read/write amplifier circuit which reads and writes data from and to memory cells selectively pointed to by the row decoder circuit 102 and the column decoder circuit 103, reference numeral 105 denotes an internal data input/output line, reference numeral 106 denotes an external data input/output line, reference numeral 107 denotes a data input/output circuit which inputs and outputs data from and to the sense read/write amplifier circuit 104, reference numeral 108 denotes a row address, reference numeral 109 denotes a column address, and reference numeral 110 denotes an address control signal.
Reference numeral 111 denotes an address input circuit which selectively outputs a row address 108 specifying a row to the row decoder circuit 102 and a column address 109 specifying a column to the column decoder circuit 103 according to an address control signal 110; reference numeral 112 denotes an external control signal; reference numeral 113 denotes a control circuit which sends out an address control signal 110 according to an external control signal 112; reference numeral 114 denotes an internal address control signal; reference numeral 115 denotes a refresh circuit which produces an internal address control signal 114 equivalent to an address control signal 110 during standby to effect the refresh operation of the memory cell region 101; reference numerals 116's denote timing adjustment signals; reference numeral 117 denotes a timing generator circuit which adjusts the timings of the operations of the address input circuit 111, the control circuit 113, and the refresh circuit 115 by sending timing adjustment signals 116's; reference numerals 118's denote internal synchronization clock signals; reference numeral 119 denotes a clock generator circuit which synchronizes the data input/output circuit 107, the address input circuit 111, the control circuit 113, the refresh circuit 115, and the timing generator circuit 117 by sending internal synchronization clock signals 118's; and reference numeral 120 denotes an external clock signal.
Reference numeral 121 denotes a memory array region comprised of the components 101 to 107, reference numeral 122 denotes a control region comprised of the components 108 to 120, reference numeral 123 denotes a semiconductor memory device comprised of the memory array region 121 and the control region 122 as the component circuit according to the invention, reference numerals 124's denote large-scale logic circuit regions comprised of standard cells, reference numeral 125 denotes a redundancy saving address storage unit, reference numeral 126 denotes a redundancy saving address line which connects the redundancy saving address storage units 125 and the memory array region 121, reference numerals 127's denote external terminals connected to the semiconductor memory device 123 and the large-scale logic circuit regions 124's, and reference numeral 128 denotes the semiconductor device comprised of the semiconductor memory device 123, the large-scale logic circuit regions 124's, the redundancy saving address storage unit 125, and the external terminals 127's.
Since the present invention is directed to the configuration of the above semiconductor memory device, detailed descriptions about the operations of the circuits of FIG. 9 will be omitted.
FIG. 10 is an explanatory drawing of a conventional configuration of the semiconductor memory device 123 shown in FIG. 9. In FIG. 10, reference numeral 201 corresponds with the memory array region 121, reference numeral 202 corresponds with the control region 122, reference numerals 203's correspond with the data lines 106's, and reference numeral 204 corresponds with the external control signal 112 and the external clock signal 120.
Since the control region 202 is placed so as to become equal in length to the memory array region 201, the control region 202 has a high aspect ratio (see JP-A No. 2002-324395).
However, in a case where large-capacity DRAMs are made as hard macros while meeting such a basic specification, imbalances in dimensional ratios between components have become pronounced as control circuits have been miniaturized due to advanced microfabrication process.
FIG. 11 is an explanatory drawing of the configuration of main wirings presented by placing the components of the control region 122 of FIG. 9 in the control region 202 of FIG. 10. In FIG. 11, reference numeral 301 denotes an address input circuit, reference numeral 302 denotes a control circuit, reference numeral 303 denotes a refresh circuit, reference numeral 304 denotes a timing generator circuit, reference numeral 305 denotes a clock generator circuit, reference numeral 306 denotes an address control signal, reference numeral 307 denotes an internal address control signal, reference numeral 308 denotes a timing adjustment signal, and reference numeral 309 denotes an internal clock signal. In FIG. 11, those connecting signals are drawn beside the circuits for purposes of illustration; however, it can be easily seen that those are implemented by forming plural wiring layers and connecting layers on the circuits laid out in actuality. Since the aspect ratio of the entire control region 122 is high as is clear from FIG. 11, the signal wirings 306 to 309 increase in length in the direction of their long side, thereby a wiring delay time lengthens and speed performance degrades. And further, although the areas of the logic circuits 301 to 305 constituting the control region 202 can be reduced with the square of the scaling law due to advanced microfabrication process, the direction of the long side is limited by the miniaturization of the memory cells because the pace of the miniaturization of the memory cells constituting the memory array region 201 is slow as compared with the pace of the miniaturization of the transistors constituting the logic circuits, and therefore the area of the semiconductor memory device cannot be optimally shrunken.
Furthermore, since there is also such a limitation on the wiring layers, the degree of freedom in their connection lowers and performance in the timings of the operations of the circuits degrades. That is, the effects of the performance of the semiconductor memory device and reducing the layout area of the semiconductor memory device are decreased, and finally the effect of reducing the production cost of the semiconductor device resulting from its miniaturization is decreased.